Dynamic frequency band allocation between radio communication networks

ABSTRACT

Methods and apparatus relate to cellular communications and in particular to a frequency spectrum shared by two cellular networks. An object is flexible utilization of the spectrum. This is achieved by a method where a first of the networks occupies part of the shared spectrum in relation to the traffic load in the first network. The first network informs a second of the networks on the extent the shared spectrum is occupied, for the second network to be free to use the shared spectrum outside the occupied part. A radio resource management unit, a base station controller, and a radio base station are also disclosed. An advantage is that spectrum can be lent from an old system when a new system is introduced.

This application is a continuation of and claims the benefit of thefiling date of U.S. patent application Ser. No. 12/522,510 filed on Jul.8, 2009, which is a 371 of International Application PCT/SE2007/050019filed on Jan. 15, 2007, both of which applications are incorporated hereby reference.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to cellular radio communications ingeneral and more particular to a method for utilizing a frequencyspectrum band shared among two or more radio networks. The inventionalso relates to a control node for performing the method, to an RRMnode, to a base station controller and a radio base station comprisingthe RRM node.

DESCRIPTION OF RELATED ART

In traditional planning of cellular networks, a range of contiguousradio frequencies, referred to as a carrier, are allocated in a staticfashion to a single radio network. This is illustrated with thefrequency axis in FIG. 1, where Carrier 1, ranging from frequency f1 tof3, is allocated to Cellular Network 1 and Carrier 2, that ranges fromfrequency f2 to f4 is allocated, to Cellular Network 2. Between the twocarriers, a Guard-Band is typically included in order to reduce thespurious emissions emitted between the cellular networks.

As a consequence of this traditional deployment the traffic belonging tocellular network 1 is kept entirely in carrier 1 and the trafficbelonging to cellular network 2 is kept entirely in carrier 2.

Since there is no overlap between the two carriers decisions about thescheduling of data on carrier 1 can be taken by cellular network 1without any information about the scheduling of cellular network 2 andvice versa. One example of the above is where cellular network 1 is aGSM network belonging to operator A and cellular network 2 is a GSMnetwork belonging to operator B. Another example will be when cellularnetwork 1 is a GSM network and network 2 is an LTE network and the twonetworks 1 and 2 belong to the same operator. This is illustrated in thetime/frequency axis of FIG. 2.

Operators will need an increased flexibility in their cellulardeployments in the coming years for several reasons:

-   -   An increased number of cellular technologies ate available    -   The need to migrate spectrum from their currently deployed        cellular technology (e.g. GSM) to more modern cellular        technology (e.g. LTE).    -   Shortage of spectrum will certainly be a problem for some        operators, it is often expensive to get access to.    -   A general trend of “technology agnosticism” from regulators,        whereby the allocation of frequency bands to operators does not        prescribe the usage of any particular technology.

SUMMARY OF THE INVENTION

The object of the present invention is flexible utilization of aspectrum by two networks.

In the first radio network an RRM unit control the radio resourcemanagement in one or more cell, and in the second network a second RRMunit controls the radio resource management in one or more cell. Thebasic concept of the invention is to occupy part of a spectrum for usein the one or more cell/s controlled by the first RRM unit in relationto the traffic load in the cell/s controlled by the first RRM unit. Thesecond RRM unit is informed of the occupied part of the shared spectrum,and is free to use the shared spectrum outside the occupied part.

The invention also relates to a first RRM unit with an interface forconnection to the second RRM unit, and that has means for performing themethod.

The invention further relates to a base station controller, and a radiobase station including the RRM unit.

An advantage with the invention method is a superior utilization of theshared spectrum.

In particular it is an advantage when a new network based on newtechnology is introduced. The frequency band dedicated to the newnetwork may be too narrow to allow for the highest bitrates affordableby the technology itself. The frequencies of the shared spectrum thenmake the highest bitrates possible.

A further advantage exampled by the GSM and LTE networks is that thatthe average bitrates in the LTE system, as seen by the end-user, aresubstantially higher than they would be if LTE was confined to a part ofthe spectrum that is dedicated to the LTE-network only.

Yet another advantage of the invention is a radio network that is sharedbetween two different network operators. In this embodiment twooperators may share one RBS. At least one part of the spectrum in whichthe RBS operates its radio communication is then shared between the twooperators so that the RBS can use the shared part of the spectrum eitherfor radio communication to mobile stations attached to the first networkoperator or for radio communication attached to the second networkoperator.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a frequency axis illustrating the prior art usage of thespectrum bands.

FIG. 2 is the same as FIG. 1, except for illustrating an inventive usageof spectrum.

FIG. 3 is a time/frequency diagram illustrating spectrum utilization oftwo separate bands by a GSM and an LTE network.

FIG. 4 is the same as FIG. 2, whereas illustrating an alternativespectrum utilization.

FIG. 5, is a view of some nodes, and cells of two Networks.

FIG. 6 is a block diagram of nodes in a GSM and an LTE system.

FIG. 7 is a flowchart of the steps of a first method embodiment.

FIG. 8 block diagram of nodes in a GSM and an LTE system and a controlnode.

DESCRIPTION OF PREFERRED EMBODIMENTS

The invention is based on a frequency band being divided into tree part,as is depicted by the frequency axis in FIG. 2. The frequency band f1-f2is allocated to a first network, the frequency band from f3-f4 isallocated to a second network, albeit part f3-f2 of the allocated bandsare shared by both networks and the first network has only a part f1-f3of carrier dedicated for its own and the second network only part f2-f4of carrier dedicated. In the lower part of FIG. 2 the respective RRM(Radio Resource Manager) of the networks are marked by boxes. The RRMcontrol the usage of the spectrum and are connected for communicatingthe usage of the shared spectrum between each other.

The core of the invention is the exchange of information messagesbetween the first and the second network which allows each system toknow which part of the shared spectrum that is eligible for trafficscheduling. These information messages can be either proprietary orstandardized.

The advantage of the spectrum allocation can be understood by comparisonof FIG. 3 that discloses prior art allocation a spectrum to a GSM and anLTE net, and its usage by the GSM traffic in a time/frequency diagram,with the spectrum allocation and usage in FIG. 4, illustrating theinventive allocation to the nets in the same type of diagram. Tomaintain an acceptable grade of service, i.e. a low blocking rate, theoperator is forced to allocate bandwidth to GSM for traffic peaks to behandled within the spectrum allocation. With static spectrum allocation,as in the prior art, this limits the bandwidth allocation to LTE. Bysharing part of the spectrum the LTE system can get access to it, andget a large part of it, during the time periods when the traffic in GSMis low or medium. Thereby the LTE can offer a substantially largercapacity and peak rate.

FIRST EMBODIMENT

The inventions primary application is for scenarios where both networksbelong to the same operator.

FIG. 5, is a view of a first cell C1 in a GSM system and a second cellC2 in an LTE system. The first cell C1 is served by radio base station15 in the GSM system, i.e. a GSM BTS, 15, and the second cell C2 isserved by an LTE RBS 12 (radio base station). The GSM BTS, 5, isconnected to a GSM BSC (Base Station Controller) 13. The GSM BSC, 13,and the LTE RBS, 12, have links for data communication via a corenetwork. For this invention the links are not important. Important isinstead, a new link connecting the GSM BSC, 13, with the LTE RBS 12, andthat will be described further down.

Of course GSM and LTE networks comprise numerous cells and base stations15, 12. FIG. 5 is for illustrative purposes of two networks, controlledby the same operator, sharing part of spectrum and having at least somecells with overlapping geographical coverage as is the case with thefirst and the second cell C1, C2. This complicates the interferencesituation.

FIG. 5 is a block diagram, illustrating functional blocks of the GMS BTS5, the GSM BSC, 13, and the LTE RBS, 12 that are essential for theinvention.

The functional blocks in the GSM BSC, 13, are the GSM radio resourcemanager 2, the Channel handler 3, the group switch 4 and the signalingentity 6 that communicates with the LTE system via the LTE signalingentity 7. The GSM BTS, 5, includes the important modules Radio unit 5and antennas. The LTE RBS contains the functional blocks SignalingEntity 7, radio resource manager 8, the Scheduler 9, the data buffer 10,the radio unit 11 and the antennas. The functional blocks of the GSMBSC, 13, and LTE RBS, 12, are with exception of the radio unit 11,primarily implemented as software executed by processors. They mayhowever to a various extent be implemented by hardware. The extent ischoice of implementation. The functional units, 2-4, 6-11, are typicallyimplemented in separate physical program and processors, however some ofthe functional units may share physical entity.

In the first embodiment the GSM system has priority in the snaredspectrum but lets the LTE system know, by means of the informationelements sent between from the GSM RRM, 2, to the LTE RBS RMM, 8, whichparts of the shared spectrum are used by GSM and when. The LTE systemwould then maintain up to date information about which part of theshared spectrum is presently occupied by GSM and schedule LTE data inthe remaining part of the spectrum. This function will be described inmore detailed with reference to FIG. 6 and to the steps of a methodillustrated by the flowchart of FIG. 7.

The GSM RRM, 2, controls both the spectrum that has been dedicated toGSM only, i.e. the carrier between frequencies f1 and f3 in FIG. 2, andthe spectrum that has been allocated to both GSM and LTE, i.e. theshared spectrum between frequencies f3 and f2 in FIG. 2.

Initially the GSM REM, 2, takes frequencies from the shared spectruminto use based on the traffic load in the GSM network, see S1 in FIG. 7.

In following step S2, the GSM RRM, 2, signals to the GSM signalingentity, 6, what frequencies in the shared carrier are presently in useby the GSM radio network. The GSM signaling entity, 6, sends aninformation element containing this information to the LTE signalingentity which forwards this message to the LTE RRM, 8.

In S3, the LTE RRM 8, processes the information with other availableinformation about which frequencies to use and sends the resulting radioresource information to the LTE scheduler, 9. In particular the LTE RRM,8, instructs the scheduler, 9, not to use any of the frequencies in theshared carrier that is presently being occupied by GSM. The LTEscheduler, 9, uses this information in combination with other availabledata to determine which user data in the data buffer, 10, shall betransmitted to the mobile stations and which resources, such asfrequencies, shall be used. In particular the scheduler, 9, uses onlythe frequencies that are indicated as available by the LTE RRM, 2.

The traffic load of the GSM is monitored, S4, and compared to upper andlover thresholds, S5. This is performed by the GSM RRM, 8.

In case of a decrease in the GSM traffic load, the first step is againentered by the GSM RRM, 2, releasing some of the frequencies occupied byGSM. The steps following on the first step S1 is performed in a loop.

In an alternative step 4 and 5, S4, S5, the channel handler, 3, receivesa request for a new voice call to be set tip in the GSM cell. Thechannel handler, 3, signals this request to the RRM, 2, which determinestraffic load increase.

If step 5, S5, results in a increase of the GSM load, the GSM RRM, 2, ina sixth step S6, identifies a GSM radio channel that can be used andstores information about which frequencies that GSM channel requires.The GSM radio resource manager sends a message to the LTE resourcemanager. The message contains information about the frequencies that aregoing to be used for the GSM call and instructs the LTE system to notuse these frequencies for scheduling traffic.

The LTE RRM, 8, acknowledges receipt of the information, and theacknowledgement is received by the GSM RRM, 2, the seventh step S7.

Next, see S8, the GSM RRM, 2, grants the channel handler to set up thevoice call on the identified frequencies. The channel handler, 3, usesstate of the art methods to set up the voice call through the groupswitch over the abis interface via the GSM BTS, 5, and over the radiointerface to the motile using the radio channel granted to the call bythe GSM REM. In parallel, to the voice call set up, the LTE signalingentity, 7, informs the LTE RRM about the frequencies that are from nowon used for the GSM voice call. The LTE RRM relays this information tothe LTE scheduler which immediately stops all scheduling on thecorresponding frequencies.

When the last step is performed the traffic in the GSM system ismonitored, see step S4, and the further steps are performed in a loop.

SECOND EMBODIMENT

FIG. 8 is block diagram, of the same nodes as FIG. 6 with the exceptionof a control node, 14, external the GSM and LTE network nodes. Thecontrol node, 14, has interfaces connecting to the signaling entities,6, 7, of the GSM BSC, 13, and LTE RBS, 12, via links 21. All thefunctional units, 2-4, 6-15, of the GSM BSC, 13 and the LTE RBS, 12 arethe same as in FIG. 6, albeit the functioning of the RRMs being somewhatdifferent.

In the second embodiment, the GSM is not privileged over the LTE in theaccess to the shared network. The LTE RRM, 8, monitors the traffic loadand if the load cannot be handled within the frequency spectrum alreadyassigned by the control node, 14, the LTE RRM, 8, requests the controlnode, 14, to assign more of the shared spectrum to the LTE system. TheGSM RRM, 2, functions in the same way. The request on spectrumallocation from the LTE and GSM RRM, 2, 8 includes a measure of therespective the traffic load.

When the control node, 14, has received the request, to be assigned moreof the shared spectrum from the LTE RRM, 8, the control node, 14,request the GSM RRM, 2, to provide a measure of the GSM traffic load.The control node, 14, compares the traffic loads of the GSM and LTEnetworks.

Based on the information about the load in the GSM and LTE networksrespectively, present spectrum allocations and policies as defined bythe network operator the control node, 14, decides whether or not thepresent allocations of the shared spectrum to the GSM REM function andLTE RRM functions shall foe changed. If the decision of the RRM controlnode, 14, is to re-assign (change) then both the RRM, 2, 8 of the GSMand LTE networks are informed. If the decision is to do nore-assignment, then only the LTE RRM, 8, is informed because it made therequest.

Traffic Load Measures and Policy Parameters

The control node, 14, in the second embodiment need to compare thetraffic load measures from the LTE and GSM systems. The measures shouldbe processed by the respective RRM, 2, 8, to be comparable. The measurescould for example be based on any of the parameters: occupation ofavailable radio channels, packet loss over radio, delays, throughput ineither the uplink or downlink direction or any combination of theparameters. Preferably, the measure is quantified in relation to thefrequencies already assigned.

The load measures can be either of the form of instantaneous load level,load level as filtered over a well-defined time period which could rangefrom milliseconds to minutes or even hours. Alternatively the loadmeasures could be predictions of the load situation for a future timeperiod.

The load measures could be sent periodically frost the RRM units 2 and 8to the central RRM control function 14. Alternatively the load measurescould be sent based on events, e.g. a significant change in the loadsituation in either of the GSM and LTE system as compared to lastreported load measure.

The policy parameters serve the purpose to compare end weigh theimportance of the load measures in the decision about how to re/assignspectrum to the RRM units 6 and 8. The policy parameters are either apermanent part of the RRM control unit 14 or provisioned to the RRMcontrol unit 14, e.g. by means of an operation and management system.The policy parameters could e.g. compare two conceptually different loadmeasures such as number of ongoing voice calls in GSM to the channeloccupancy of LTE or weigh two comparable measures such as channeloccupancy in the two systems. In one embodiment of the invention thepolicy parameters are used to prioritize one network, over the otherwhich in the extreme limit of absolute priority to GSM gives a functionsimilar to embodiment one of the invention discussed in previoussections.

The policy parameter can also be connected to QoS (Quality of service)policies of the individual end-users in the two systems so that spectrumis assigned based on services and individual user priorities.

Further Alternatives to the Embodiment

It should be understood that the RRM, 2, of the GSM system could beconnected to plural RRM, 8, in respective LTE RBSs, 12. Thereby, the GSMRRMs, 2, could be connected to a number of LTE RBS, 12, that correspondin number and geographical coverage to a number of GSM BTS, 15, that arecontrolled by the GSM BSC, 13.

The GSM and LTE networks are examples of networks used in the first andsecond embodiment. Networks based on other radio access technologies canof course be used in combination with the present invention. For examplethe invention would be advantageously when migrating from a networkbased on CDMA technology to a network based on OFDM or any other futureaccess technology. The RRM, 2, or the control node, 14, could furtherallocate the uplink and the downlink spectrum separately.

Other systems may divide there functional entities differently than thatof the GSM. BSC, and give other names to the entities.

The networks sharing a spectrum could also be based on the same accesstechnology. This is in particular the case for the scenario when thecontrol node, 14, assigns the shared spectrum to a network that offersthe highest price for access the shared spectrum. Moreover, it could bepossible to share a spectrum by more than two networks.

ABBREVIATIONS

-   LTE Long Term Evolution of 3 G as is standardized by 3GPP-   OFDM Orthogonal Frequency Division Multiple Access-   RBS Radio Base Station-   RRM Radio Resource Manager-   BTS Base Transceiver Station

The invention claimed is:
 1. A method of controlling utilization of afrequency spectrum shared by first and second radio networks that eachinclude one or more radio resource manager (RRM) units for controllingradio resource management in one or more cells, comprising: occupying afirst part of the shared frequency spectrum for use in one or more cellsin the first radio network that are controlled by a first RRM unit,wherein the occupied first part is in relation to a traffic load in theone or more cells controlled by the first RRM unit; and informing asecond RRM unit in the second radio network of the first part of theshared frequency spectrum, for the second RRM unit to be free to use theshared frequency spectrum outside the first part in one or more cellscontrolled by the second RRM; wherein a first geographical area coveredby the one or more cells controlled by the first RRM unit and a secondgeographical area covered by the one or more cells controlled by thesecond RRM unit at least partly overlap, and the first and second radionetworks use the same radio access technology.
 2. The method of claim 1,further comprising adapting the first part of the shared frequencyspectrum in relation to traffic load changes in the one or more cellscontrolled by the first RRM unit.
 3. The method of claim 1, furthercomprising adapting the first part of the shared frequency spectrum inrelation to the traffic load in the one or more cells controlled by thesecond RRM unit.
 4. The method of claim 2, wherein the second RRM unitis informed of any adaptation of the occupied first part of the sharedfrequency spectrum.
 5. The method of claim 3, wherein the first RRM unitis informed of any adaptation of the occupied first part of the sharedfrequency spectrum.
 6. The method of claim 1, wherein the method isperformed by the first RRM unit.
 7. The method of claim 1, wherein oneof the first and second radio networks is a GSM network, and the otherof the first and second radio networks is an orthogonal frequencydivision multiplex network.
 8. A radio resource manager (RRM) unit forcontrolling radio resource management functions in one or more cells ina first radio network, comprising: an interface adapted for connectionto a second RRM unit in a second radio network; and a device configuredto perform a method as defined by claim
 1. 9. The RRM unit of claim 8,wherein the interface is adapted for connection to plural RRM units inthe second radio network.
 10. The RRM unit of claim 8, wherein the RRMunit is included in a base station controller.
 11. The RRM unit of claim8, wherein the RRM unit is included in a radio base station.
 12. The RRMunit of claim 10, wherein the base station controller is included in acellular network.
 13. The RRM unit of claim 11, wherein the radio basestation is included in a cellular network.
 14. A control node,comprising: a first interface adapted for a connection over a link to afirst radio resource manager (RRM) unit in a first communicationnetwork; a second interface adapted for a connection over a link to asecond RRM unit in a second communication network; and a processoradapted to perform a method as defined by claim 1, wherein occupying isbased on traffic load measures received at least from the first RRMunit, and the processor is further adapted to inform the first andsecond RRM units of the occupied first part of the shared frequencyspectrum via the first and second interfaces.